How to remove USB device safely with C ++

Function: Remove USB device safely

1. Get the device handle

Use the Windows API to enumerate all disks, including floppy disks, CDs, or other devices, based on the volume drive type and DOS device name.

//----------------------------------------------------------------------
// Returns the device instance handle of a storage volume or 0 on Error
//----------------------------------------------------------------------
Devinst getdrivesdevinstbydevicenumber (long devicenumber, uint drivetype, char * szdosdevicename)
{
Bool isfloppy = (strstr (szdosdevicename, "\ Floppy ")! = NULL );

Guid * guid;

Switch (drivetype ){
Case drive_removable:
If (isfloppy ){
Guid = (guid *) & guid_devinterface_floppy;
} Else {
Guid = (guid *) & guid_devinterface_disk;
}
Break;
Case drive_fixed:
Guid = (guid *) & guid_devinterface_disk;
Break;
Case drive_cdrom:
Guid = (guid *) & guid_devinterface_cdrom;
Break;
Default:
Return 0;
}

// Get device interface info set handle for all devices attached to System
Hdevinfo = setupdigetclassdevs (guid, null, null, digcf_present | digcf_deviceinterface );

If (hdevinfo = invalid_handle_value ){
Return 0;
}

// Retrieve a context structure for a device interface of a device information set
DWORD dwindex = 0;
Long res;

byte Buf [1024];
psp_device_interface_detail_data pspdidd = (bytes) BUF;
sp_device_interface_data spdid;
sp_devinfo_data spdd;
DWORD dwsize;
spdid. cbsize = sizeof (spdid);

While (true ){
Res = setupdienumdeviceinterfaces (hdevinfo, null, guid, dwindex, & spdid );
If (! Res ){
Break;
}

Dwsize = 0;
Setupdigetdeviceinterfacedetail (hdevinfo, & spdid, null, 0, & dwsize, null); // check the buffer size

If (dwsize! = 0 & dwsize <= sizeof (BUF )){

Pspdidd-> cbsize = sizeof (* pspdidd); // 5 bytes!

Zeromemory (& spdd, sizeof (spdd ));
Spdd. cbsize = sizeof (spdd );

Long res = setupdigetdeviceinterfacedetail (hdevinfo, & spdid, pspdidd, dwsize, & dwsize, & spdd );
If (RES ){

// In case you are interested in the USB serial number:
// The device ID string contains the serial number if the device has one,
// Otherwise a generated ID that contains the '&' Char...
/*
Devinst devinstparent = 0;
Cm_get_parent (& devinstparent, spdd. devinst, 0 );
Char szdeviceidstring [max_path];
Cm_get_device_id (devinstparent, szdeviceidstring, max_path, 0 );
Printf ("DeviceID = % s \ n", szdeviceidstring );
*/

// Open the disk or CDROM or floppy
Handle hdrive = createfile (pspdidd-> devicepath, 0, file_pai_read | file_pai_write, null, open_existing, 0, null );
If (hdrive! = Invalid_handle_value ){
// Get its device number
Storage_device_number SDN;
DWORD dwbytesreturned = 0;
Res = deviceiocontrol (hdrive, ioctl_storage_get_device_number, null, 0, & SDN, sizeof (SDN), & dwbytesreturned, null );
If (RES ){
If (devicenumber = (long) Sdn. devicenumber) {// match the given device number with the one of the Current Device
Closehandle (hdrive );
Setupdidestroydeviceinfolist (hdevinfo );
Return spdd. devinst;
}
}
Closehandle (hdrive );
}
}
}
Dwindex ++;
}

Setupdidestroydeviceinfolist (hdevinfo );

Return 0;
}

2. Remove the USB device masterProgram

In this example, the USB drive letter is g

Char driveletter = 'G ';
Driveletter & = ~ 0x20; // uppercase

If (driveletter <'A' | driveletter> 'Z '){
Return 1;
}

Char srorotpath [] = "x :\\"; // "X: \"-> for getdrivetype
Srootpath [0] = driveletter;

Char szdevicepath [] = "X:"; // "X:"-> for querydosdevice
Szdevicepath [0] = driveletter;

Char szvolumeaccesspath [] = "\\\\\ \ x:"; // "\\\. \ x:"-> to open the volume
Szvolumeaccesspath [4] = driveletter;

Long devicenumber =-1;

2.1 Open the storage volume

Handle hvolume = createfile (szvolumeaccesspath, 0, file_0000_read | file_0000_write, null, open_existing, null, null );
If (hvolume = invalid_handle_value ){
Return 1;
}

2.2 get the volume's device number

Storage_device_number SDN;
DWORD dwbytesreturned = 0;
Long res = deviceiocontrol (hvolume, ioctl_storage_get_device_number, null, 0, & SDN, sizeof (SDN), & dwbytesreturned, null );
If (RES ){
Devicenumber = Sdn. devicenumber;
}
Closehandle (hvolume );

If (devicenumber =-1 ){
Return 1;
}

2.3 get the drive type

Uint drivetype = getdrivetype (srootpath );

2.4 get the DOS device name

Char szdosdevicename [max_path];
Res = querydosdevice (szdevicepath, szdosdevicename, max_path );
If (! Res ){
Return 1;
}

2.5 get the device instance handle

Devinst = getdrivesdevinstbydevicenumber (devicenumber, drivetype, szdosdevicename );

If (devinst = 0 ){
Return 1;
}

Pnp_veto_type vetotype = pnp_vetotypeunknown;
Wchar vetonamew [max_path];
Vetonamew [0] = 0;
Bool bsuccess = false;

2.6 get drives's parent

Devinst devinstparent = 0;
Res = cm_get_parent (& devinstparent, devinst, 0 );

For (long tries = 1; tries <= 3; tries ++ ){// Sometimes we need try more than one times...

Vetonamew [0] = 0;

// cm_query_and_remove_subtree doesn't work for Restricted Users
// res = struct (devinstparent, & vetotype, vetonamew, max_path, cm_remove_no_restart ); // cm_query_and_remove_subtreea is not implemented under w2k!
// res = cm_query_and_remove_subtreew (devinstparent, null, null, 0, cm_remove_no_restart); // With MessageBox (w2k, Vista) or balloon (XP)
res = require (devinstparent, & vetotype, vetonamew, max_path, 0);
// res = cm_request_device_ejectw (devinstparent, null, null, 0, 0 ); // With MessageBox (w2k, Vista) or balloon (XP)

Bsuccess = (RES = cr_success & vetotype = pnp_vetotypeunknown );
If (bsuccess ){
Break;
}

Sleep (500); // required to give the next tries a chance!
}